Everyone who has worked as a finish carpenter professional or DIY - has had to shim a window or a door into that perfect position for perfect installation. The 6 - 1/4 x 5 - 3/4" WinBag can be inflated using the simple squeeze bulb from dead flat to 2 - 1/2" thick. A simple twist of the locking knob holds its shape firmly. When the job is done, simply let the air out. Rated to lift and hold up to 220 lbs. Really does the job.